Background: There are few studies that compare measures of diagnostic accuracy for selected waist cutoff points and the criteria of abdominal obesity given by the International Diabetes Federation (IDF) and the National Cholesterol Education Program (NCEP). Methods and Results: The present study utilized data from the Third Korean National Health and Nutrition Examination Survey. Analyses for receiver-operating characteristic (ROC) curve were performed with data for 4,677 men and women aged 20-80 years who reported being free of a physician-diagnosed cardiovascular disease or cancer. On the basis of measures of diagnostic accuracy, including minimum distance to ROC curve and Youden index, waist circumference of 84-86 cm for men and of 78-80 cm for women were found to be optimal cutoff points. The study also demonstrated that the use of smaller waist circumference for diagnosis of the metabolic syndrome decreases discrepancies between the prevalence of the IDF-defined metabolic syndrome and that of the NCEP-defined metabolic syndrome. Conclusions: Waist circumference of 90 cm, the cutoff point given by the IDF for Asian men, may not be an appropriate value for Korean men, while its cutoff point for Asian women is appropriate for Korean women. (Circ J 2009; 73: 2068-2075)